The present invention related generally to oscillators and resonators. In particular, the invention provides a method and apparatus for fabricating and operating a resonator coupled to a CMOS substrate. More particularly, one or more single crystal silicon oscillator structures are controlled by a CMOS substrate in an embodiment. In a specific embodiment, at least a portion of the resonator structure is fabricated from a single crystal layer joined to the CMOS substrate through a wafer-level layer transfer process. Other embodiments of the present invention have a much broader range of applicability.
Quartz resonators have been used for oscillators and/or sensing devices. For example, quartz resonators are widely used in oscillators found in watches and other applications that benefit from small size, low cost, and ruggedness. A quartz resonator operates by resonating in response to a stimulus, which may be a physical event, such as acceleration, force, or pressure. Alternatively, the quartz resonator may resonate in response to an electrical signal, thereby acting as a frequency source.
In addition to quartz resonators, microelectromechanical systems (MEMS) have been utilized to fabricate structures implementing resonator designs. As an example, silicon materials, which are characterized by excellent mechanical strength and high material quality, have been used in various MEMS resonators. Silicon is an attractive material for MEMS resonators, not only due to its favorable material properties, but as a result of benefits gained by leveraging existing semiconductor processing techniques. Based on processing techniques developed by the integrated circuit industry, fabrication processes for silicon-based MEMS resonators are generally well developed.
Despite the developments made in the field of MEMS resonators, there is a need in the art for improved methods and systems for silicon-based resonators and oscillators.